Monthly Guide for Growing Dahlias in the Bay Area

by Deborah Dietz, assisted by Ted & Rose Marr

Dormant December

We start Dahlia Calendar with December because December is the end and beginning of Dahlia Seasons. End for this season and the beginning for the next. Getting off on the right step is critical for next year’s crop.
Dig-out: Dig up your dahlias by keeping as much dirt around each clump as
possible. Shovel STRAIGHT DOWN and cut a 1ft. radius around your plant. This will sever any extended roots. Using 2 shovels placed on either side of the clump (or pitch forks or a combination of both), gently lift up the root mass. DO NOT extricate by pulling up on the stalk portion—this could break the necks of the tubers. Instead, scoop up the tuber clump from beneath with your hands.An alternative method is to dig a moat around the clump so you know how far the tubers extend.(Read more in Dec. 2003 , Dec. 2004 DSC eNewsletters on how to handlethe dig-out without breaking the tubers. See how DSC Members do a dig-out at the dahlia dell.Processing: After you have pulled up your clumps, you have two choices on what to do with them.
1. Process them immediately: Dig, divide, bleach, dab with sulphur or Captan and store in vermiculite, cedar shavings or peat moss. Or…2. Process them in Spring: Maintain as much dirt around your tuber clump as possible, put the whole megalith in a cardboard box. Close the box and stack in a cool but not freezing spot until March. This method avoids dividing the clump immediately. Wait until spring when the “eyes” are more obvious or when little shoots appear. The dividing spots are then more obvious.(Read more in Dec. 2003, Dec. 2004DSC eNewsletters on how handle the entire process).Hands on lesson: Best place to learn how to process a dug out clump is to come to the November meeting when digging, dividing and over-wintering tubers are the main topics.
The DSC Big Dig, which occurs every year around the second or third weekend in January, provides another perfect hands on opportunity.Pre-prepare the soil: As soon as your clumps are up, the new season begins. Start by spreading compost lavishly. Some people plant a cover crop of vetch or fava beans which nitrogenates the soil as well as covers up the ugly brown patch.DSC Activities in December: Lopping Day, Christmas Party,Annual Membership Fee due.

Jumpstart January

This is the month to prepare your soil and plan what dahlias to grow. Soil preparation consists basically of weeding and fortifying with compost and fertilizer.

Weed: The more assiduously you eradicate unwanted green things now, the fewer you’ll have to deal with come planting time. Keep the weeds obliterated; a little work now saves backbreaking labor later.

Plotting the Patch: Plot your plot to determine what new dahlias you need for next season. Dream through dahlia catalogs, cruise the Dahlia Addict, and contact the suppliers. Order from these suppliers whom DSC members are satisfied customers. Start negotiating with DSC members for scions of their jewels from last season.

DSC Activities in January: The DIG OUT and Information, Getting Tubers Started Indoors.

Fuss February

Anticipating spring, get your dahlia tubers germinating and pot-tuber cuttings ready to go. Regardless of your facilities, start germination indoors. Giving the plants a head start will produce blooms even as early as May!

Greenhouse: Find a sunroom, bathroom, loft, basement or garage with sufficient lighting. There are lots of way to build an indoor greenhouse. The easiest and least expensive is Tinnee’s method.

Planting to Germinate: Time to milk carton. Use a mixture of 1/3 potting soil, 1/3 sand & 1/3 vermiculite or perlite or just commercial potting mix. Lay the tuber on its side as though it were taking a nap. Have the eye pointing up. Make sure you label the flap accurately with the name of the plant. Place them by warm windows or by the water heater. Some of the A’s and AA’s need a lot of heat to sprout. If you are space challenged, close and stack the cartons until they sprout. Be sure to check regularly.Water: Start out with the soil slightly moist, do not water at all until green sprouts appear. Then, spritz sparingly. Spritz with water or even with Miracle Grow. Remember, there are very few roots yet to absorb water, so be sparing. Use a mulch to help the soil retain the moisture.

Order more Plants: Last chance to order from catalogs. For details see January.Interesting Tip: Sprinkle double poppy seeds around the flower beds. These colorful flowers cover the bare brown earth until replanting.

DSC Activities in February: Information on planting, cutting, and propagation, ADS new introductions

Cuttings: When there are more than one shoot coming out of a tuber, cut the extra one off or germinate it for another plant.

See “How to grow more plants from multiple shoots of one tuber by Lou Lombardo.”

DSC Activities in March: Overview information on planting Dahlias

Arresting April

An exciting month, this is the month you can finally start to plant.
There is also the DSC Annual Tuber and Cutting Sale!
Hardening off: Before you plant into the ground, harden off the young plants.When your milk cartoned dahlias are 8”+ high, begin putting them outside during the day. Eventually you can leave them out overnight. They are then “hardened off” and ready to plant.You can make individual greenhouses by erecting a stick in the middle of your container and tenting the whole thing with a clear plastic bag.
Planting – Finding a right spot: When the plants are about 18″ tall, plant them in the ground. The location should have sunshine for at least 6 hours each day. Place the plants 30″+ apart. In hot areas, choose a spot with morning sun only. Try to ascertain which are your potentially tallest dahlias, place them in the back, your little twitchy dahlias in the front.
Dig a hole 6-8” deep; mix in a balanced fertilizer (10-10-10, 16-16-16). We do not recommend planting rootless tuber into the ground directly. If you must, absolutely avoid watering until the shoots appear above the ground.Planting – Preparing the spot: Dahlias like well drained soil so augment your soil with organic material such as compost and chicken manure. You can also add 2-3 lbs of 5-10-5, or 10-10-10, or 16-16-16 fertilizer per 100 sq. ft (1/4 lb per 10 square feet). Avoid getting the fertilizer on the plants directly. Rake the fertilizer into the soil and then water. Label and stake:Insert a 4-6 ft stake into the ground at the edge of the hole before the tuberous roots are planted. Dahlias are large plants and require support. Label the stake immediately. The tall cultivars cannot support themselves and plant breakage will occur without support.
DANGER DANGER: As soon as the plants are in the ground, on the same day protect your young plants from snails and slugs by sprinkling snail bait as directed.Watering: Watering varies depending on whether you are planting a dahlia plant from a tuber or from a cutting.Plants from tubers – never over water and do not leave stagnant water around young plants from tubers. Sprouted tubers from milk cartons should be watered immediately upon planting. Watch for signs of drying depending on the weather.Plants from cuttings- need watering almost daily as they have wee roots and no tuber to sustain them.
Water at the soil level, no overhead watering.Insurance: Remember to keep 30-50% extra dahlias as insurance. If you plan to plant 20, keep 4 to 10 in milk cartons as back up. Bring the extras to DSC meetings in May for sale or
give them away.DSC Activities in April: Tuber and plant sale third Saturday of April.

Munchingly May

May is the month to watch your dahlias take shape, start to mature and journey on for another year of glorious blooms.
Watering: Water at soil level (do not use overhead spray) once every 3-4 days. Water deeply each time but do not leave any stagnant water. Remember tubers & cuttings need drastically different levels of watering. Cuttings rely on new roots, necessitating frequent quenching; tubers start with no roots, so should only be watered sparingly.Fertilize: Remember to fertilize with a well balanced fertilizer (10-10-10) about once every 3 weeks. Surround delicate plants with individual milk carton sheaths to protect from sun and wind exposure.Protect from pests: Apply liberally with slug, snail and earwig bait, succulent new leaves lure voracious bugs from everywhere. Diligently monitor and eradicate undesirable pests.Bushy Plants: Your plants will grow tall rapidly.
To encourage the plants to grow more branches cut off the tip of the center stem after the plant has three sets of leaves. As the plant matures, remove the bottom two rows of leaves. And, be sure to tie the main stem to the stake.

DSC Activities in May: Information on Fertilizing and pest control

Jubilant June

June is jubilant because your first bud or even the first bloom has arrived. Now is the time to make sure you get the best blooms.

Disbud: It is time to pinch and disbud. Certain plants harbor the first bud tightly down in the center where it would be terribly crotch-bound were it to bloom. Pinch out the first bud with the two new buds beside it.
This allows the next buds to have longer, stronger stems & encourages the plant to be a little bushier rather than too tall.
Airing the bottom: As your plant reaches 24+” begin to take off the bottom leaves, discouraging snails, slugs & mildew. Remove non-flower producing leaves to encourage growth, allow more light into the plant, and for better air circulation.

Recycle: Compost dahlia refuse carefully. Like any composting, make sure you follow the directions carefully. Lots of benefits in composting: good for the environment, obligate parasites, and good for your soil.

Fertilize: With the arrival of the first bud, it is time to switch to a different fertilizer. Using a fertilizer that has a higher phosphorous content, such as 10-30-20 will encourage more blooms.

Pest Control: Be vigilant. A bloom with deformed leaves or leaves with holes does not show well. Fend off, at all effort, snails, earwigs, etc.

Fungus: Now you will encounter for the first time, the growth cycle another difficult matter, powdery mildew. Spray a cocktail of Organocide (for aphids) and Captain Jack’s Deadbug Brew with spinosad (for leaf miners, spider mites, thrips and caterpillars), Dr. Earth Fungicide and Stylet Oil (for powdery mildew), water soluble fertilizer, and a little liquid dishwashing soap as a sticker.

DSC Activities in June: Information on photography

Jumping July

This is a busy month, the plants are budding all over. Buds, buds all over.

Find central bud and leaf pair, carefully disbud

Disbudding: Buds are popping all over. Diligently disbudding will reward you with exhibition quality blooms. Two or three headed blooms are of lesser quality because they are much smaller and can be deformed. Leave only one bud.

Deadheading: This is critical to keep your dahlia plant producing more blooms. After a Dahlia bloom opens, cut it for your indoor display. This will encourage more blooms. Even if you don’t cut it, you should dead-head it by removing it just when pollen appears for a “double” plant or when the petals begin drooping on an “open-centered” variety. Deadheading is important so new blooms would be encouraged and energy is not directed to making seeds. Always cut the bloom at a point that is one node below the bloom (the next node). This will encourage more laterals to produce more blooms.

Busy, busy doing the routines: Clean out the under leaves, spraying, watering, fertilizing, all this demands your time now. Clean out the under growth of leaves, allowing for at least 12 inches of space above the ground for good air circulation.

Pictures: Start taking pictures of early blooms to enter into the photo competition. Check out the Dahlia Dell at the Golden Gate Park as new varieties begin blooming.

DSC Activities in July: Novice only mini show

Awesome August

August is the celebratory month for Dahlia lovers. The peak of bloom is here. What an amazing sea of color and cacophony of shapes shouting at the admirers.

Exhibition: Whether it is to enter a show or just for your own enjoyment, cut early in the morning or later evening and put the bloom immediately in water. Some suggest that touching the ends in alum sustains the blooms longer.Abundance: To keep your dahlias blooming in full spate, assiduously dead head; cut your spent blooms below the set of first leaves where the new growth begins. If you fail to cut back to new growth, your plants will soon look like brown skeletons. Disbud to assure only one bloom per stem with a nice pair of leaves. Truly you get a bigger flower, longer stem, and more plant vigor if you do not let every bud blossom. Give your growing plants support. If you have the luxury of multiple stakes, you can put one on either side of your plant and wrap ties around the whole bundle. If not, string the plant staunchly to the stake to prevent wind damage and give the heavy laterals some support.

Be vigilant: Control pests, clean out lower branches, arrest fungus, fertilize, and water properly. You are ensured of a truly amazing August.

DSC Activities in August: Mini show open to all.

Scintillating September

Although peak season is over, September will continue to give you a bountiful bloom. Bestow bouquets on all your friends! Keeping the plants at top performance will not only give another couple months of pleasure but also will ensure you have a healthy crop next year.

Practice bondage: Tie up your plants or the wind will make you weep. Take the low laterals off now. They will break off when they are heavier, so get them now and send that energy to the branches where you need growth & flowers.

Keep the Bandits at bay: Aphids, caterpillars and diabolical beetles abound. Try the traditional cocktail for the first two: Malathion, Orthene, a fungicide, Superbloom, & liquid dishwashing soap applied in a sprayer. For diaBRATicas, try painting Dixie cups with Tanglefoot atop your stakes. Squishing with fingers works satisfyingly, too. If you are fighting powdery mildew, strip off the dusted leaves and spray with a MAJOR fungicide.

Water and fertilize: Water when your plants show heat fatigue; this could be once a day or once a week depending on the weather. Fertilize as needed.

Disbudding and Deadheading: Cut clear back to the next growth-producing flowers. The more rigorously you cut back, the more your plants will flourish. Also, strip off the “rags” (limp brown leaves at the bottom of bushes). The more zealously you do these things, the longer your plants will continue to bloom.

Evaluate: Time to evaluate which plant shall be replanted next year. Critically evaluate each bush. If it is substandard and not worthy of passing on its tubers, chuck the whole plant in the garbage now. If you have two or more of the same cultivar, evaluate which is superior. Make note on your label so you will know which one to replant in the spring. Transfer labels down to around the base of the plant so that they will be attached even when they are whacked in December.

DSC Activities in September: Mini show open to all

Outstanding October

Yes, October can be outstanding. Lots of blooms even so late in the season. Make October your outstanding month with surprise gift blooms to friends and at the office.Mildew: The mildew plague is upon us. Strip every affected leaf & spray with RosePride, previously called Funginex or Orthenex. Or, the systemic Orthenex, but it is nastier & more dangerous than others so be very cognizant of what you are doing and shower immediately afterwards. Wait a week & spray again. You can add some SuperBloom & dishwashing soap to your cocktail. When in question, toss out those really badly affected.Doubling the effort: As your bloom size dwindles,try double disbudding: taking off both the extra buds next to the central stem, and also the emerging shoots just below the first leaf pair.below the first leaf pair. This will channel all the energy to the remaining bloom.Water and Fertilize: Do it one more time. Fertilize one more time. Cut back to vibrant growth. If October proves warm, we may get a final flush. Don’t worry if your lovely flowers start popping center or getting a bit scraggly; they are responding to the waning light. As your plants slow down, cut back on water.Tag: Check name tags for accuracy. Move name tags down and tie them around the bottom of the plant so they will still be attached when lopping in December.Seedlings: Now is the time to consider allowing a few blooms to go to seed. Seeds are the genetic lottery; dreadful odds but such a payoff! Simply let the petals fall off; wait until the remaining seed head is brown and dry. Bring into a cool, dry area for germinating in January.DSC Activities in October: Last mini show

Nonchalant November

November is practically the end of the bloom season. If you worked real hard over the season, you will get some blooms until Thanksgiving. Time to wrap up for the year.

Stop watering: The waning seasonal light prematurely pops centers, attenuates stems, & slows down growth. Let nature take its own course and provide growth to the tubers for next year’s crop.

Labels: Make sure your labels are legible. And, move them down to the bottom of the plant.

Lopping: Lop every plant. That will give the tubers 8 weeks to toughen their skins and go dormant before digging out in December or January. Depending on how well your soil drains, you can dig them out before the first frost. When each plant turns brown, cut down to 4-5 bamboo-like notches; these act as water seals. Each bamboo-like joint is a mini water seal to help prevent crown rot. If your plants are in pots, move them to a sheltered area or cover to prevent rain from rotting them. Allow your tubers to go dormant for at least 6 weeks before disinterring. They seem to develop tougher skin if they are allowed to go fully dormant.

DSC Activities in November: Annual DSC member meeting and election of Officers. Lopping day either last weekend of November or first weekend of December.Lou P. demonstrates digout and dividing of tubers at the regular Tuesday meeting.